1. Field of the Invention
The present invention relates to a control system, and more particularly, a control system and a control method of a water-cooled multi-cylinder engine, which is utilized at a time of an overheat of the engine.
2. Description of the Related Art
In a compact four-stroke-cycle multi-cylinder engine, which is mounted, for example, to an outboard motor or like, there is provided a structure adapted to employ a water-cooled type engine cooling method. In a concrete example of a cooling water passage structure, for example, a cooling water such as a sea water, a lake water or the like sucked from a water intake port is pressurized by a water pump so as to be introduced to the engine.
In this case, when the water intake port for the cooling water is clogged by an algae or the like or a water pump gets out of order, an overheat of the engine will be caused due to shortage of the cooling water. In order to obviate such defect, there is provided a structure having a control system for executing a misfire of an ignition plug, stopping of a fuel injection or fuel supply, or like so as to reduce an engine revolution number, thereby restricting an ascent of an engine temperature.
However, in the engine provided with such control system as mentioned above, even if the engine remains the overheat state, a normal ignition and a normal injection are executed in the case where the engine revolution number becomes lower than a limited revolution number, and, hence, a normal operation would be executed.
There is no problem in the case of, for example, clogging of the water intake port or the like, which can relatively easily solved. However, in the case of a problem which is not easily solved on the scene, for example, a roughness on the sea condition, a trouble of the water pump or the like, it is obliged for the engine to be driven even in the overheat state, and in such case, the temperature of the engine will have to be further increased. Accordingly, there is a fear that an excessive damage is applied to equipment such as electrical equipment arranged in an engine main body or at a periphery thereof.
The present invention is made by taking the above matters encountered in the prior art mentioned above into consideration, and an object of the present invention is to provide a control system and a control method of an engine capable of rendering the engine usable while minimally restricting an engine damage due to an overheat.
This and other objects can be achieved according to the present invention by providing, in a general aspect, a control system of an engine of a water-cooled multi-cylinder structure, in which an engine revolution number is reduced to a level less than a restriction revolution number on the basis of at least one condition of revolution number restriction controls including a misfire and a fuel stop for all cylinders of the engine, at a time of an occurrence of an overheat of the engine, so as to restrict an increasing of a temperature of the engine, wherein in a case when the engine revolution number is less than the restriction revolution number after the overheat occurs, or the engine revolution number is lowered to be less than the restriction revolution number on the basis of the revolution number restriction control after the overheat occurs, a specific cylinder is controlled to be stopped by means of at least one of the misfire and the fuel stop.
In a preferred embodiment, the specific cylinder controlled to be stopped by at least one means of the misfire and the fuel stop corresponds to first and fourth cylinders or second and third cylinders in a case of a four-stroke-cycle 4-cylinder engine, corresponds to first and second cylinders or third and fourth cylinders in a case of a two-stroke-cycle 4-cylinder engine, and corresponds to any one of cylinders in a case of a 3-cylinder engine.
When the specific cylinder is controlled to be stopped on the basis of the occurrence of the overheat, an idle target revolution number of the engine is set to a revolution number higher than a target revolution number at a time of normal operation period.
When a reason of the overheat is cancelled during the stop control of the specific cylinder, the stop control of the specific cylinder is set to be cancelled only at a time when a shift apparatus takes a neutral.
The engine is an engine for an outboard motor in which a crankshaft is vertically arranged.
In a specified aspect, there is provided a control system of an engine of a water-cooled multi-cylinder structure for controlling an overheat (i.e., revolution number) of the engine, comprising:
an element for detecting an occurrence of an overheat of an engine;
an element for monitoring and detecting an engine revolution number;
an element for discriminating whether the detected engine revolution number exceeds or not a restriction revolution number after occurrence of the overheat; and
an element for performing an operation stop control to a specific cylinder by means of at least one condition of revolution number restriction controls including misfire and fuel stop to thereby reduce the engine revolution number.
In anther aspect, there is provided a method of controlling an engine of a water-cooled multi-cylinder structure for controlling an overheat (i.e., revolution number) of the engine, comprising the steps of:
detecting an occurrence of an overheat of an engine;
monitoring and detecting an engine revolution number;
discriminating whether the detected engine revolution number exceeds or not a restriction revolution number after occurrence of the overheat; and
performing an operation stop control to a specific cylinder by means of at least one condition of revolution number restriction controls including misfire and fuel stop to thereby reduce the engine revolution number.
According to the present invention of the aspects mentioned above, in the water-cooled multi-cylinder engine provided with the control system reducing the engine revolution number to the level less than the restriction revolution number, the structure is considered so that when the engine revolution number is less than the restriction revolution number after the occurrence of the overheat, or the revolution number is lowered to be less than the restriction revolution number on the basis of the revolution number restricting control, the specific cylinder of the engine is controlled to be stopped by at least one means of the misfire and the fuel stop. Therefore, it is possible to prevent the engine temperature from being increased even when the engine is continuously used at a time of occurrence of the overheat.
Furthermore, since the multi-cylinder engines can be controlled in accordance with the numbers of the cylinders, it is possible to obtain a stable engine revolution even when the engine is continuously used.
Furthermore, according to the preferred embodiment, it is possible to obtain a stable engine revolution even in a low revolution number range of the engine.
Furthermore, when the reason of the overheat is cancelled during the stop control of the specific cylinder of the engine, the stop control of the specific cylinder can be set to be cancelled only at a time when the shift apparatus takes its neutral position. It is therefore possible to prevent the engine revolution number from being rapidly increased after canceling the stop control.
The nature and further characteristic features will be made more clear from the following descriptions made with reference to the accompanying drawings.